1. Field of the Invention
The present invention relates to a developing device used in an image forming apparatus such as an electrophotographic copying machine, an electrophotographic laser beam printer and the like, and a process cartridge including an image bearing member and such developing device and removable with respect to the image forming apparatus.
2. Related Background Art
As shown in FIG. 4, a developing device 3 incorporated into a process cartridge C comprises a container 6 for containing toner therein, an agitating member 7 for agitating the toner in the container 6, a developing roller 9 arranged in parallel with an electrophotographic photosensitive member 1 and rotated in a direction shown by the arrow R1, a magnet roller 10 arranged within the developing roller 9, and an elastic blade 11 for regulating an amount of the toner which is fed out from the container 6 by the developing roller 9 and is conveyed toward a developing zone where an electrostatic image is developed.
As shown in FIG. 5, holders 12L, 12R are secured to left and right end walls of the container 6 of the developing device 3 by screws 13. (In the specification, the terms "left" and "right" are referred to with respect to a longitudinal direction of the developing roller.) The holders 12L, 12R have central supporting holes 15L, 15R, respectively, by which the magnet roller 10 is positioned at a fixed position. Further, the developing roller 9 is rotatably supported by the holders 12L, 12R via bearings 17L, 17R firmly fitted on inner peripheral supporting surfaces 16L, 16R of the holders 12L, 12R. The developing roller 9 comprises a cylindrical sleeve member 19, and flange members 20L, 20R secured to left and right ends of the sleeve member. Shaft portions of the flange members 20L, 20R are firmly fitted in the bearings 17L, 17R.
Further, between the left and right ends of the sleeve member 19, and the bearings 17L, 17R, there are disposed spacer rings 21L, 21R for regulating an undesired movement of the developing roller 9 in the left and right direction. Between the spacer rings, side seal members 22L, 22R made of felt or the like are disposed between the sleeve member 19 and the container 6 to seal the clearance between these members 19, 6. The side seal members 22L, 22R serve to prevent the toner in the container 6 from leaking toward both ends of the developing roller 9.
The developing roller 9 is driven via a gear 23 secured to the left flange member 20L. A rotational driving force is transmitted from a drive source (not shown) to the gear 23 via a transmitting mechanism (not shown). As shown in FIG. 4, the elastic blade 11 secured to the container 6 is elastically urged against the outer peripheral surface of the developing roller 9 along the longitudinal direction of the latter.
However, in the above-mentioned conventional technique, although the magnet roller 10 could be attached to the left and right holders 12L, 12R with high accuracy, it was difficult to mount the developing roller 9 within the left and right holders 12L, 12R and accordingly within the container 6 with high accuracy, with the result that it was feared that the delicate vibration in the rotation of the developing roller 9 arose.
Incidentally, the poor mounting accuracy of the developing roller 9 with respect to the container 6 is caused by the delicate clearance (assembling allowance) between the holders 12L, 12R and the bearings 17L, 17R. That is to say, it is necessary to provide a moderate clearance, which may be minimum, for permitting the assembling and disassembling, between the outer peripheral surfaces of the bearings 17L, 17R and the inner peripheral supporting surfaces (fitting surfaces) 16L, 16R of the holders 12L, 12R, and this clearance causes the vibration during the rotation of the developing roller 9. However, if such clearance is omitted, the assembling and disassembling operations will be made troublesome and difficult; to the contrary, the provision of such clearance worsens the accuracy of the rotation of the developing roller 9.
Due to the above-mentioned vibration or play, the positioning accuracy of the developing roller 9 with respect to the magnet roller 10, elastic blade 11, side seal members 22L, 22R and the photosensitive member 2 is worsened, thus generating the poor accurate positionings regarding the latters, which cause the unevenness in application of toner t onto the developing roller 9, the unevenness in thickness of a layer of the toner t, leakage of the toner t, and the unevenness in a toner image on the photosensitive member 2, respectively. Further, the unevenness in the quality of a copied image and the penetration of the toner t into undesired zones are caused.